We describe factors associated with poor compliance and dose reductions and examine the relative impact of compliance, dose reduction and discontinuation on graft outcome. Medicare claims for MMF in 7062 deceased donor renal recipients with at least 1 year of graft function were used to calculate compliance and dose reductions. Compliance was modeled using medication possession ratio to define quartiles for poor, low, medium and high compliance. The relative impact of compliance, dose reduction and discontinuation on graft outcome was assessed with Cox proportional hazards. Pediatric (Age 0-18, Odds ratio = 1.71, 95% CI 1.11-2.63, p = 0.014) and adolescent recipients (19-24, 1.57, 1.23-2.00, p < 0.001) were more likely poorly compliant compared to adults age 25-44. Poor compliance was also associated with physical limitations, hypertension, delayed graft function, rejection, infection and GI conditions. Poor (1.43, 1.11-1.84, p = 0.005) and low (1.46, 1.13-1.88, p = 0.004) compliance was associated with an increased hazard of graft loss as was >50% dose reduction (1.69, 1.15-2.50, p = 0.008) and discontinuation (8.34, 6.85-10.2, p < 0.001). Medication possession ratios lower than the 3-year mean were associated with an increased risk of graft loss. These results may indicate that interventions to improve compliance among kidney transplant recipients should strive for high rather than discourage low compliance.